Multiple-Capture Trap for Invasive Bullfrogs

Jug-o-rum...jug-o-rum...jug-o-rum. Once uncommon in the American southwest, the sound is now heard in many wetlands, streams and tributaries. It is the mating call of the American bullfrog. The bullfrog is native to wetland habitats in the central and eastern United States. However, during the 1900s, bullfrogs were intentionally released in many western states as a source of food for people. With their highly competitive nature and large size, American bullfrogs are eating their way through wetlands across the West. These voracious predators eat almost anything from insects and fish to other frogs, hatchling turtles, snakes and mammals.

"Outside of habitat destruction, the American bullfrog is having the biggest impact on the survival of the Chiricahua leopard frog in Arizona," notes WS State Director Dave Bergman. "If we can develop a nonlethal frog trap, it would greatly help our collaborators' efforts to protect this endangered species." To help address this and other conservation efforts, NWRC researchers Dr. Gary Witmer and Nathan Snow tested the effectiveness of a nonlethal, multiple-capture trap for use on bullfrogs. The trap was originally designed in Australia for use with invasive cane toads. Several types of lures were used, including light, crickets, and shiny metal flashers. Fishing lures (without hooks) hanging from the top of the traps appeared to be the most effective. The floating traps were quite successful, capturing as many as seven bullfrogs in one trap. However, many bullfrogs were observed near the traps and were never captured, indicating the need to develop more effective lures. Furthermore, even though bullfrog call and night spot-lighting counts suggested a slight decline in the pond's population, many bullfrogs remained in the pond after five days of trapping.

"One benefit of the nonlethal floating trap is it allows for the removal of non-target species," states Gary Witmer. "This becomes critical when your talking about the protection of endangered amphibians, such as the Chiricahua leopard frog."

No non-target animals were captured during the course of the study. It is possible, however, that any non-target animals in the traps at the same time as bullfrogs might be consumed by the voracious bullfrogs.